Many different types of pneumatic valve structures employing digital valves are known. Many of these structures are complicated and somewhat difficult to program. Consider, for example, the devices described in U.S. Pat. No. 3,550,630, issued Dec. 29, 1970, to Hugo A. Panissidi, and also U.S. Pat. No. 3,777,776, issued Dec. 11, 1973, to Monique Boisserand.
Among some of the problems encountered in this art are providing a multiple valve structure which is essentially simple and relatively easy to program. If separate electronic to pneumatic valves of an ordinary type having continuous air flow are provided, an excessively large capacity of air flow need be provided.